Electrode 10-20 system

  • EEG electrode transforms ionic current into electrical current using pre-amplifiers.
  • Silver - Silver chloride are commonly used in electrode disc.
  • Reusable scalp disc or cup electrode are placed on head using conductive gel.
  • The area is first cleaned with alcohol to remove skin oils.
  • Amplitude frequency and phase of EEG depends on electrode placement.
  • This placements include frontal, parietal, temporal and occipitinal cranial areas.
  • The head is marked at four standard points nasion(nose), inion(back head) & left & right preauricular points(ears).
  • Nineteen electrodes plus one for grounding is used.
  • For EEG the electrodes are placed at 10%,20%, 20%, 20% and 10% from inion to nasion along lenght.
  • Electrode is made either unipolar or bipolar form.
  • Unipolar contains scalp-leads connected to common point like ear lobes.
  • A bipolar scheme is available by interconnecting scalp electrodes.

Unipolar EEG recording mode:

Bipolar EEG recording mode:

Average EEG recording mode: